This application is being cofiled with Ser. No. 09/922,273, related to a random color array film.
1. Field of the Invention
This invention relates to a process for forming a color filter array on a surface wherein colored beads composed of a water-immiscible synthetic polymer or copolymer are coated from a water-borne solid particle dispersion.
2. Background of the Invention
The great majority of color photographs today are taken using chromogenic color film in which color-forming couplers, which may be incorporated in the film or present in the processing solution, form cyan, magenta and yellow dyes by reaction with oxidized developing agent which is formed where silver halide is developed in an imagewise pattern. Such films require a aid development process which is carefully controlled in respect of time and temperature, which is usually followed by a silver bleaching and a fixing step, and the whole process typically takes several minutes and needs complex equipment.
Color photography by exposing a black-and-white photographic emulsion through a color filter array which is an integral part of the film or plate on which the photographic emulsion is coated, has long been known to offer certain advantages of simplicity or convenience in color photography. Thus the Autochrome process, disclosed by the Lumiere brothers in 1906 (U.S. Pat. No. 822,532) exposed the emulsion through a randomly disposed layer of red, green and blue-colored potato starch grains, and the emulsion was reversal processed to give a positive image of the scene which appeared colored when viewed by light transmitted through the plate. The process allowed the formation of a colored photograph without the chemical complexity of later photographic methods.
The Dufaycolor process (initially the Dioptichrome plate, L. Dufay, 1909) used a regular array of red, green and blue dyed patches and lines printed on a gelatin layer in conjunction with a reversal-processed black-and-white emulsion system, which similarly gave a colored image of the scene when viewed by transmitted light.
Polavision (Edwin Land and the Polaroid Corporation, 1977) was a color movie system employing a rapid and convenient reversal processing method on a black-and-white emulsion system coated above an array of red, green and blue stripes, which gave a colored projected image. It was marketed as a still color transparency system called Polachrome in 1983.
These methods suffered a number of disadvantages. The images were best viewed by passing light through the processed film or plate, and the image quality was not sufficient to allow high quality prints to be prepared from them, due to the coarse nature of the Autochrome and Dufaycolor filter arrays, and the coarse nature of the positive silver image in the Polavision and Polacolor systems. The regular array patterns were complicated and expensive to manufacture. In addition, the films which used regular or repeating filter arrays were susceptible to color aliasing when used to photograph scenes with geometrically repeating features.
U.S. Pat. No. 4,971,869 discloses a film with a regular repeating filter array which claims to be less susceptible to aliasing problems. The film comprises a panchromatic photographic emulsion and a repetitive pattern of a unit of adjacent colored cells wherein at least one of the cells is of a subtractive primary color (e.g. yellow, magenta or cyan) or is of a pastel color. Scene information can be extracted from the developed film by opto-electronic scanning methods.
U.S. Pat. No. 6,117,627 discloses a light sensitive material comprising a transparent support having thereon a silver halide emulsion layer and a randomly arranged color filter layer comprising colored resin particles. The material has layer arrangement limitations and results in increased fogging of the sensitized layer. The patent discloses the preparation of a color filter array using heat and pressure to form the color filter layer prior to application of the light sensitive layer to a support. Due to the necessary use of pressure and heat, it is not practical to use the teachings of this patent to prepare a film having a light sensitive layer between the color filter layer and the support. Attempting to apply the needed heat and pressure to bond the filter layer to the rest of the multilayer would damage the light sensitive layer. The patent also discloses exposing, processing and electro-optically scanning the resultant image in such a film and reconstructing the image by digital image processing.
Color photographic films which comprise a color filter array and a single image recording layer or layer pack have the advantage of rapid and convenient photographic processing, as the single image recording layer or layer pack can be processed rapidly without the problem of mismatching different color records if small variations occur in the process. A small change in extent of development for example will affect all color records equally. Exceptionally rapid processing is possible using simple negative black-and-white development, and if suitable developing agents are included in the coating, the photographic response can be remarkably robust or tolerant towards inadvertent variations in processing time or temperature.
It is desirable that the method of manufacturing the filter array be simple and of comparatively low cost. Known methods of making regular filter arrays, such as those known for Dufaycolor or Polachrome films, are complex and costly, involving several sequential applications of materials to the film. Known methods of making random filter arrays, such as those used for Autochrome film and that described in EP 935 168 also involve complex operations, including separating and grading or sizing the colored particles of starch or resin respectively, dispersing them in a coating medium, coating and drying and then calendaring the coated layer to flatten the particles.
A problem to be solved is to provide a process for forming a color filter array on a surface that is simple and cost effective.
The invention provides a process for forming a color filter array layer on a transparent surface, comprising the step of applying a water-borne solid-particle dispersion of randomly disposed colored beads of a water-immiscible synthetic polymer to the surface.
In the case of digital image capture, devices such as digital cameras and scanners, the method of the invention can provide a low cost means of manufacturing color filter arrays, and the random nature of the array will give reduced color flinging at the edges with fine geometric structures in the scene relative to a regular array.